Clearance regulation of mechanical gas face seals: Part I - modeling

Anew state space model is presented for coned face flexibly mounted stator (FMS) mechanical gas face seals. The model employs an analytical representation of the linearized gas film stiffness and damping properties. States are defined for the generalized gas film force modes and the mechanical dynamic modes. The state space formulation is convenient for determining stability limits and also allows for efficient time domain simulation as compared to simulations where convolution integrals must be computed or full numerical simulations employing the Reynolds equation must be utilized. The modeling techniques are applied to a noncontacting mechanical gas face seat, the stability limit is found, and simulation results are compared to a full numerical simulation utilizing the Reynolds equation. The simulation results validate the developed model. The state space model is utilized in Part II to Perform controllability and observability analyses and to design reduced order observers to estimate states that cannot be measured and robust tracking controllers to regulate the seal clearance to maintain system stability.